Hydrogenation process for the preparation of 1,2-diols

Abstract

Disclosed is a process for the preparation of 1,2-glycols by hydrogenation of 1,2-dioxygenated organic compounds in the presence of a catalyst composition comprising a ruthenium compound, a trivalent phosphorus compound selected from 1,1,1-tris(diarylphosphinomethyl)alkyl or substituted alkyl, and a promoter selected from Lewis acids, protic acids having an ionization constant (K i ) of 5×10 −3 or greater, and onium salts. The process is useful for the hydrogenation of glycolic acid or derivatives thereof to ethylene glycol.

1. A process for preparing a 1,2-diol, which comprises contacting a 1,2-dioxygenated organic compound, with the exception of oxalic acid or ester thereof, with hydrogen, under hydrogenation conditions, in the presence of a catalyst composition comprising:
 (a) a ruthenium compound; 
 (b) a trivalent phosphorus compound selected from 1,1,1-tris(diarylphosphinomethyl)alkyl or substituted alkyl; and 
 (c) a promoter selected from Lewis acids, protic acids having an ionization constant (K i ) of 5×10 −3  or greater, onium salts, and mixtures thereof; 
 
       wherein said catalyst components (a)-(c) are dissolved in an organic solvent, to produce a 1,2-diol. 
     
     
       2. The process according to  claim 1 , wherein the 1,2-diol comprises ethylene glycol, 1,2-propylene glycol, 1,2-butanediol, or a mixture thereof. 
     
     
       3. The process according to  claim 1 , wherein the 1,2-dioxygenated organic compound comprises glyoxal, glycolic acid, glycol aldehyde, glycol aldehyde dimer, glycolic acid ester, methyl glycolate, oligomers of glycolic acid, oligomers of glycolic acid ester, lactic acid, lactic acid ester, oligomers of lactic acid, oligomers of lactic acid ester, 2-hydroxy butyric acid, esters of 2-hydroxy butyric acid, oligomers of 2-hydroxy butyric acid, or mixtures thereof. 
     
     
       4. The process according to  claim 1 , wherein the ruthenium compound is selected from ruthenium carboxylates, ruthenium acetylacetones, ruthenium hydride complexes, ruthenium carbonyl compounds, ruthenium halides, ruthenium oxides, ruthenium phosphine complexes, and mixtures thereof; and the trivalent phosphorus compound is selected from tris(diphenylphosphinomethyl)alkyl or substituted alkyl. 
     
     
       5. The process according to  claim 4 , wherein the ruthenium compound comprises ruthenium(III)acetylacetonate. 
     
     
       6. The process according to  claim 1 , wherein the trivalent phosphorus compound comprises 1,1,1-tris(diphenylphosphinomethyl)ethane. 
     
     
       7. The process according to  claim 1 , wherein the promoter is selected from ammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, tetraphenylphosphonium bromide, sodium tetraphenyl borate, ammonium tetrafluoroborate, tetramethyl ammonium tetrafluoroborate, toluenesulfonic acid, phosphoric acid, triflic acid, sulfuric acid, methanesulfonic acid, trifluoroacetic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and mixtures thereof. 
     
     
       8. The process according to  claim 7 , wherein the promoter is selected from tetrabutylammonium hexafluorophosphate, triflic acid, toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and mixtures thereof. 
     
     
       9. The process according to  claim 1 , wherein the organic solvent is selected from alcohols, ethers, hydrogenation starting materials, and hydrogenation reaction products. 
     
     
       10. The process according to  claim 9 , wherein the organic solvent is selected from methanol, ethanol, propanol, butanol, isobutanol, isopropanol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propanediol, neopentyl glycol, 2-ethylhexanol, 1,4-butanediol, diethylene glycol, triethylene glycol, glycerol, hexanol, octanol, methoxy ethanol, diisopropyl ether, dipropyl ether, and mixtures thereof. 
     
     
       11. The process according to  claim 10 , wherein the organic solvent comprises methanol, ethylene glycol, 2-methyl-1,3-propanediol, 2-ethylhexanol, hexanol, octanol, or mixtures thereof. 
     
     
       12. The process according to  claim 1 , wherein said hydrogenation conditions comprise a temperature of 125° C. to 220° C., and a hydrogen pressure of 1500 psig to 3000 psig. 
     
     
       13. A process for preparing ethylene glycol, which comprises contacting glycolic acid or a derivative thereof with hydrogen, under hydrogenation conditions, in the presence of a catalyst composition comprising:
 (a) ruthenium(III)acetylacetonate; 
 (b) 1,1,1-tris(diphenylphosphinomethyl)ethane; and 
 (c) a promoter selected from tetrabutylammonium hexafluorophosphate, triflic acid, toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and mixtures thereof; 
 
       wherein said catalyst components (a)-(c) are dissolved in a solvent selected from methanol, ethylene glycol, 2-methyl-1,3-propanediol, 2-ethylhexanol, hexanol, octanol, and mixtures thereof; to produce ethylene glycol. 
     
     
       14. The process according to  claim 13 , wherein said glycolic acid derivative is selected from methyl glycolate, oligomers of glycolic acid, and mixtures thereof. 
     
     
       15. The process according to  claim 13 , which further comprises separating the ethylene glycol from the catalyst components and recycling the catalyst components to the contacting step.